Commutator assembling process



R. F. JUDISCH COMMUTATOR ASSEMBLING PROCESS Nov. 10, 1931.

Filed July 3, 1929 air/e Ewe/ Z7, 1 M

Patented Nov. '10, 1931 UNITED STATES PATENT OFFICE ROBERT F. JUDISC H,OF CANTOII OHIO, ASSIGNOR TO THE' HOOVER COMPANY, A CORPORATION OF OHIOCOMMUTATOR ASSEMBLING PROCESS Application filed July 3,

The present invention relates to commutators, and more particularly tothe process of assembling commutators for dynamo electric machines, andhas for its object an improved, more economical and simplified method ofsuch assembly.

More specifically the present invention relates to an improved method ofassembling commutators whereby, through the treatment of certain parts,certain steps of the usual commutator assembly process may be omitted.

In the drawings: V

Figure 1 is a view partially in cross section through a commutatorconstructed in accordance with the present invention.

Figure 2 is a fragmentary cross sectional view of a sector of thecommutator shown in Figure 1, the section being taken upon the line 22.

The commutator disclosed in Figures 1 and 2 comprises the parts found inthe usual commutator, including the commutator shell 1, shownaspositioned upon a'motor shaft, and having the annular clamping jaw 2,the clamping ring 3, which is positioned upon the member lHand held inplace thereon in any suitable manner, as by the turning of the end ofthe shell 1 as shown at 4, insulating collars 5 and 6, made of mica orsimilar insulating material, and commutator. segments 7 of copper whichare positioned between the jaw 2 of the shell 1 and the clamping means3, and separated therefrom by the insulating collars 5 and 6;. As in theusual commutator construction the segments 7 are .separated one fromanother by insulating seg ments 8. Grooves 9, such as would be obtainedby a saw out, are provided in the ends of the 40 commutator segments orbars 7 within each of which the end of an armature lead 10 is positionedand secured by soldering. .The.

aforedescribed pairs comprise the usual commutator construction and noinvention is clalmed in their bodily arrangement.

. In the operation of an electric machine possessing a commutator, as inDC. generators and motors, commutation is an essential factor determininthe characteristics and the performance of the machine. It is 1929.Serial No. 375,631.

brushes upon the commutator, with the resulting Wear of the copper barsand the cat ing away of said bars by the sparking, re-

sults in the lowering in height thereof at a rate faster than that ofthe insulating segments which separate them. As soon as parts of theinsulating segments extend above ,the copper segments poor commutationresults, since the brush jumps from one high point to another, makinginsuflicient contact with the copper bars, and causing increasedsparking and inefficient. operation. Electrical manufacturers haveresorted, in their ef- I fort to maintain satisfactory commutation,tothe undercutting of the commutator, which is, in effect, the reductionof the height of the insulating segments which separate thecurrent-carrying segments. This undercutting is accomplishedby the use,in some instances, of a hand tool, which is passed between the coppersegments and which cuts away the insulator, and in other instances bythe use of a revolving circular saw, which runs the length of thesegments and which serves to cut away the insulator. In eitheroperation, and particularly the latter, a portion of the copper segmenton each side of the insulation segment is removed, through thecarelessness of the workmen, in the first instance, and through theimpossibility of maintaining the saw in exact alinement with theinsulating segment, in the second instance.

In the past it has not been possible to use insulating bars of lesserheight than that of the copper bars to effect the required relation ofsegment heights, for the reason hereinafter set forth. Thecurrent-carrying leads which come from the armature of the ma-- chine,and which are indicated in the drawings by the reference character 10,are attachedeach to a separate commutator segheres not only to the leadsand to the areas adjacent thereto within the grooves 9, but also alloyswith the copper bars along their length, and frequently bridges acrossthe slot between adjacent bars, which results, if not removed, in theshort-circuiting of the bars involved and failure of commutation. Thisdifiiculty has been overcome in the past by the undercutting operation,which both reduced the height of the insulating segments and served toremove any undesired metallic connections between bars.

The operation of undercutting was therefore required, not only to lowerthe height of the insulation segments but also to insure the absence ofthe injurious solder deposits. In the construction of "a commutator inaccordance with the present invention, the insulating segments may bemade initially of a lesser height than the current-carrying coppersegments, so that when positioned in the commutator shell and clampedthere by the clamping ring they do not project to the surface of thecommutator, but present the desired undercut formation without thenecessity of the sawing or cutting by hand.

According to the present invention the current-carrying copper bars,either before or after their assembly in the commutator shell, butbeforetheir exposure to the solder for the purpose of attaching the armatureleads, are provided with a solder-resistant coating, a preferred mannerof carrying out the step belng to form a film of oxide thereon, as byheating in air or by dipping in a chemical solution. In order that anarmature lead may be attached, a slot 9 is made in each bar or segment,as by a saw out, after the copper segment has been oxidized, resultingin a new unoxidized surface in the cut to which the solder will adhere,the proper flux being applied to the lead and the adjacent unoxidizedsurface. in the slot. The entire commutator may be dipped into thesoldering solution with the wires positioned in their grooves, as shownin Figure 1, and the solder will adhere only to the lead and theadjacent area in the groove 9 in the copper bar 7 which has been freshlycut and has beensave that at-which the armature lead contacts,

because, as described above solder will'not adhere to an oxidizedsurface. As the insulating segments usedin'the assembly are of a heightless than that of the copper segments, the desired relative height ofthe segments is effected, and as the possibility of short-circuitingsolder connections between the copper bars is eliminated, there is nonecessity for the undercutting operation, the omission of that stepresulting in economy of time and the preservation of the originalcommutator bar width heretofore lessened somewhat by the undercuttingoperation. 7

It will be understood that the solder-resistant coating may be anysuitable coating 80 which will prevent the adhesion of solder, which canbe conveniently formed, which will not. materially interfere with theformation of the grooves 9, and which may be conveniently removed fromthe outer brushcontacting surface of the commutator after it isassembled and connected. For instance, a film of waterglass', or anyother suitable solder resistant material, might be applied instead offorming an oxide coating, and the terms used herein are intended to beinterpreted to include any suitable means to secure the result stated.

In assembling and connecting the commutator, in accordance with thepresent invention, therefore, the expensive and unsatisfactoryundercutting of the commutator is eliminated, and the desired separationbetween the copper bars is obtained without the use of the slow andexpensive method here- 100 tofore required.

I claim 11 The process of assembling and connecting'commutatorscomprising assembling commutator bars and insulation segments upon 10: acommutator shell, and securing them in place thereon, treating theassembly to form a solder-resistant coating on'all but a por tion of theexposed surface of each of said bars, positioning the current carryingleads 11'. adjacent to uncoated surfaces of their correspondingcommutator bars, and exposing the entirecommutator as a whole to asolder to secure said leads to said bars.

2. The process of assembling and connect- 115 ing commutators comprisingassembling upon a commutator shell commutator bars and in-- sulationsegments of a height less than that of said bars, and arrangedalternately with said bars, treating the assembly to form upon thecommutator bars a coating to which solder will not adhere, providing anuncoated surface on each of said bars, positioning current-carryingleads each adjacent the uncoated surface of its corresponding commutatorbar, and soldering said leads to saidbars.

3. The process of assembling and connecting commutators comprisingassembling commutator bars and insulation segments in 211- ternaterelation upon a commutator shell and securing them in place thereon,treating the whole assembly to form a solder-resistant coating upon saidbars, forming a slot in each bar, positioning a current-carrying lead ineach slot and dipping the assembly in a solder to secure said leads tosaid bars.

4. The process of assembling and connecting commutators comprisingassembling commutator and insulation segments upon a commutator shelland securing them thereon, oxidizing the assembled commutator shell andsegments to prevent the adherence to the commutator segments of foreignmatter, providing an unoxidized surface on each of said bars andconnecting the current-carrying leads to said unoxidized surface of saidbars.

5. The process of assembling and connecting commutators comprisingassembling on a suitable retainer commutator bars and insiilationsegments of lesser height than that of said bars, and arranged,alternatel with said bars, treating the assembly to orm a I coating onsaid bars to which solder will'not adhere for the purpose of preventingthe interconnection-of said bars by solder, forming a slot in each barbelow the brush-contacting surface thereof which will be uncoated,ositioning a current-carrying lead in eac of said slots, and bathing thecomplete assembly in solder to secure the leads in the slots.

Si ned at North Canton, in the county of Star and State of Ohio, this27th day of June, 1929. 5 ROBERT F. JUDISCH.

